WO2016060500A2

WO2016060500A2 - Positive electrode catalyst for lithium-air secondary battery, method for manufacturing same, and lithium-air secondary battery comprising same

Info

Publication number: WO2016060500A2
Application number: PCT/KR2015/010916
Authority: WO
Inventors: 강용묵; 강승호; 송경세
Original assignee: 동국대학교 산학협력단
Priority date: 2014-10-15
Filing date: 2015-10-15
Publication date: 2016-04-21
Also published as: US20170301924A1; KR101621060B1; WO2016060500A9; WO2016060500A3; KR20160044699A

Abstract

Disclosed are a positive electrode catalyst for a lithium-air secondary battery, a method for manufacturing the same, and a lithium-air secondary battery comprising the same. An embodiment of the present invention provides a method for manufacturing a positive electrode catalyst for a lithium-air secondary battery, the method comprising the steps of: forming a first solution by adding a titanium ion precursor to a solvent, followed by stirring; forming a second solution by adding an organic material to a solvent, followed by stirring; forming a nanofiber composite by mixing the first solution and the second solution and then spinning the mixed solution; and forming titanium oxide (Ti0₂) nanofibers by thermally treating the nanofiber composite.

Description

【Specification】

[Name of invention]

Cathode catalyst for lithium-air secondary battery, preparation method thereof, and lithium-air secondary battery comprising same

Technical Field

One embodiment of the present invention relates to a cathode catalyst for a lithium-air secondary battery, a manufacturing method thereof, and a lithium-air secondary battery including the same. Background Art

Recently, as resource and environmental problems such as depletion of fossil fuel and global warming have emerged, interest in renewable energy is increasing. In particular, large-scale, high-power, high-energy energy storage devices are being used in the entire industry such as electric vehicles (EVs), hybrid electric vehicles (HEVs), portable power storage devices, and distributed power supplies. Battery development is a major issue in the industry because of the need.

Lithium-ion batteries have become a major player in rechargeable batteries, surpassing the previously developed nickel cadmium or nickel-hydrogen batteries due to their high energy density and long life of 75-160 Wh / kg. Lithium ion batteries are being actively researched to realize greater capacity and output in line with the demands of modern society, and are expected to develop lithium ion batteries with energy densities up to 250 Wh / kg. However, in the case of electric vehicles, the need for an energy storage device having a high energy density of 700 Wh / kg or more is required to emerge a new battery system.

Among the newly proposed various battery systems, lithium air secondary batteries have a high output of 10 times higher than lithium secondary batteries, and are environmentally friendly by using oxygen, which is infinitely present in nature, as an active material. ， The lithium-air secondary battery has a significantly lower exchange efficiency (Round-tr ip ef fi ciency) because the voltage required for layer charging is higher than the voltage emitted by the battery. There is a problem that it is difficult to secure life characteristics and reliability. In order to improve this problem, it is important to improve the exchange efficiency by reducing the overvoltage during oxygen reduction reaction and oxygen evaporation reaction by using a catalyst on the anode.

Therefore, ^' development of a catalyst in a lithium-air secondary battery is an important factor, and the development of a catalyst suitable for a lithium-air secondary battery is an early stage and requires intensive research.

[Detailed Description of the Invention]

[Technical problem]

One embodiment of the present invention, to provide a cathode catalyst for lithium-air secondary battery, a method for producing the same, and a lithium-air secondary battery including the same to improve the oxygen reduction reaction and oxygen evaporation reaction of the lithium-air battery. .

Technical Solution

One embodiment of the present invention, after adding the titanium ion precursor to the solvent, stirring to form a first solution; Adding the organics to a solvent, followed by stirring to form a solution of about 12; After mixing the first and second solutions, spinning the mixed solution to form a nanofiber composite; And heat treating the nanofiber composite to form titanium oxide (τ) ₂ ) nanofibers.

After the titanium ion precursor is added to the solvent, stirring to form a first solution; may be performed at room temperature for 0.5 to 2 hours.

The titanium ion precursor is titanium isopropoxide (Ti tanium i sopropoxide), titanium butoxide (Ti tanium butoxi de), titanium chloride (Ti tanium chlor ide), titanium nitride (Ti tanium ni tr i de), and titanium Carbide (Ti tanium carbide) may include one or two or more selected from the group consisting of.

When the titanium ion precursor is titanium isopropoxide, the method may further include adding 20 to 30 mol% of acetic acid to the first solution. The solvent may include an alcoholic solvent.

After adding the organic material to the solvent, stirring to form a second solution; may be performed at room temperature for 0.5 to 2 hours.

The organic material may include one or two or more selected from the group consisting of polyvinyl pyrrol i done, polymethyl methacryl ate, and polystyrene.

The solvent may include an alcohol solvent, acetone, distilled water (¾0), or a combination thereof.

The molar ratio of the organics to the solvent may be 0.05 to 0.08. After mixing the crab 1 and the second solution, spinning the mixed solution to form a nanofiber composite; In the mixing, the molar ratio of the organic material to the titanium ion precursor may be made from 0.2 to 0.5 .

The spinning process may be performed by electrospinning. Heat-treating the nanofiber composite to form titanium oxide (Ti0 ₂ ) nanofibers; may be performed for 1 to 7 hours in an oxidizing atmosphere, and 400 to 800.

The titanium oxide ( _T i0 ₂ ) nanofibers may have a one-dimensional structure.

The one-dimensional nanofibers may be anatase titanium oxide nanofibers (Anatase Ti0 ₂ nano f iber), rutile titanium oxide nanofibers (Rut ile Ti0 ₂ nano f iber), or a combination thereof.

The anatase titanium oxide nanofibers may be prepared by calcining the nanofiber composite at 400 to 500 for 1 to 2 hours.

The rutile titanium oxide nanofibers may be prepared by calcining the nanofiber composite at 750 to 800 for 5 to 7 hours.

Another embodiment of the present invention provides a cathode catalyst for lithium-air secondary batteries manufactured by the method for preparing the cathode catalyst for lithium-air secondary batteries described above.

Another embodiment of the present invention, the lithium-air secondary battery positive electrode including the above-described positive electrode for lithium-air secondary battery; cathode; Electrolyte; And it provides a lithium-air secondary battery comprising a separator. 【Effects of the Invention】

According to one embodiment of the present invention, titanium oxide (Ti0 ₂ ) is made of one-dimensional nanofibers to improve the oxygen reduction reaction and evaporation reaction by improving the positive electrode catalyst for lithium-air secondary battery having excellent electrochemical properties, and a method of manufacturing the same, and It is possible to provide a lithium-air secondary battery comprising the same.

[Brief Description of Drawings]

FIG. 1 is an X-ray diffraction analysis result of anatase titanium oxide nanofibers and rutile titanium oxide nanofibers according to an embodiment.

2 is a scanning electron microscope analysis result of the anatase titanium oxide nanofibers according to an embodiment.

3 is a scanning electron microscope analysis result of rutile titanium oxide nanofibers according to an embodiment.

Figure 4 is a transmission electron microscope analysis of the blue Anathas titanium oxide nanofibers in one embodiment.

5 is a transmission electron microscope analysis of rutile titanium oxide nanofibers according to an embodiment.

6 shows an initial capacity of a lithium-air battery according to another embodiment.

FIG. 7 is a diagram showing differential curves of an initial cycle charged and discharged at 200 mA / g (carbon) of a lithium-air battery according to another embodiment.

8 is a view showing a capacity-limited lifetime characteristics based on the carbon weight specific capacity 1000mAh / g (carbon) of the lithium-air battery according to another embodiment. 9 is a view illustrating Nyqui st characteristics of a lithium-air battery according to another embodiment.

[Best form for implementation of the invention]

Hereinafter, the present invention and embodiments will be described in detail. However, this is presented as an example, whereby the present invention is not limited and the present invention is defined only by the scope of the claims to be described later. Throughout the specification, when a part is said to "include" any component, it means that it can further include other components, except to exclude other components unless specifically stated otherwise. The present invention relates to a cathode catalyst for a lithium-air secondary battery capable of improving oxygen reduction reaction and oxygen evaporation reaction of a lithium-air battery, a method for preparing the same, and a method for manufacturing a lithium-air secondary battery including the same.

One embodiment of the present invention, after adding a titanium ion precursor to the solvent, stirring to form a crab 1 solution; Adding the organic to the solvent, followed by stirring to form a second solution; After mixing the first and crab solutions, spinning the mixture solution to form a nanofiber composite; And heat treating the nanofiber composite to form titanium oxide ( _T i ₀₂ ) nanofibers. It provides a method for producing a cathode catalyst for a lithium-air secondary battery comprising a.

More specifically, in one embodiment of the present invention, after the titanium ion precursor is added to the solvent, stirring to form a first solution; may be performed at room temperature, 0.5-2 hours, preferably Preferably 1-1.5 hours. In this case, when the stirring is performed for less than 0.5 hours, there is a problem that the titanium ion precursor is not sufficiently dissolved in the solvent, and when it is performed for more than 2 hours, there is a problem that titanium is precipitated.

Herein, the titanium ion precursors include titanium isopropoxide, titanium tan oxide but titanium chloride, titanium nitride, and titanium nitride. Carbide (Ti tanium carbide) may be one containing one or two or more selected from the group consisting of.

In addition, the solvent may include an alcohol solvent. The alcohol-based solvent may be, for example, ethanol.

In this case, when the titanium ion precursor is titanium isopropoxide, 20-30 mol of acetic acid is added to the first solution to prevent the titanium isopropoxide from being precipitated in the process of forming the first solution. The addition process of% may be performed. In one embodiment of the present invention, after adding to the organic solvent, the step of stirring to form a second solution; As in the above-mentioned step of forming the first solution, the phase is 0.5 (2 at room temperature It may be carried out for a time, preferably 1-1.5 hours. At this time, when the stirring is carried out in less than 0.5 hours, there is a problem that the organic material is not dissolved in the solvent, and when carried out for more than 2 hours there is a problem deviating from the viscosity in the second solution.

Here, the organic fire may include one or two or more selected from the group consisting of polyvinyl pyrrol i done, polymethyl methacrylate, and polystyrene. .

In addition, the solvent may include an alcoholic solvent, acetone (acetone), distilled water (¾0), or a combination thereof. The alcohol solvent may be, for example, methanol (methanol) ᅳ propane (butanol), butanol, isopropyl alcohol (i sopropyl al cohol, ΙΡΑ) and the like.

At this time, the molar ratio of the organic material to the solvent may be 0.05-0.08, preferably 0.06. If the molar ratio of the organic material to the solvent is less than 0.05, beads (beads) are formed, and if it exceeds 0.08, the thickness of the titanium oxide (Ti0 ₂ ) nanofibers described below is too thick. .

In one embodiment of the present invention, after mixing the first and second solutions, spinning the mixed solution to form a nanofiber composite; In the above-described process, the first solution and the second solution After mixing at a predetermined rate, nanofiber composites are formed through process control for spinning.

Here, the predetermined ratio is preferably a molar ratio of the organic matter in the second solution to the titanium ion precursor in the first solution is 0.2-0.5. When the molar ratio of the organic material to the titanium ion precursor is less than 0.2, there is a problem in that the titanium oxide (Ti0 ₂ ) nanofibers are not formed or the length of the nanofibers is formed very short, and in the case of exceeding 0.5, titanium oxide (Ti0 ₂ ) There is a problem that the thickness of the nanofibers becomes too thick.

At this time, the spinning process may be performed by electrospinning (el ectrospinning). Electrospinning includes: a supply for supplying a solution, a spinneret for spinning a solution supplied through the feeder, a collector for collecting fibers spun through the spinneret, and a voltage for applying a voltage between the spinneret and the collector An electrospinning apparatus including a generator may be used, and a fiber form may be manufactured by supplying an organic / inorganic solution to the feeder and then applying a voltage. This has the advantage of being relatively easy to synthesize the fiber-like material compared to the conventional bottom-up method such as CVD, PVD, or other top-down method.

Process control conditions for the electrospinning may include the speed of pushing the mixed solution, the rated voltage, the distance between the needle and the aluminum foil collected, the thickness of the needle, and the like. For example, it is preferable that the speed of pushing the mixed solution is 0.4 to 0.6 ml / h, the voltage is 14.5 to 15.5 kV, the distance between the needle and the aluminum foil is 8 to 10 cm, and the thickness of the needle is 23 to 25 gauge. .

In one embodiment of the present invention, the step of heat-treating the nanofiber composite to form titanium oxide (Ti0 ₂ ) nanofibers; may be performed for 1-7 hours in an oxidizing atmosphere in the air, and 400-700. In this case, when the heat treatment silver is less than 400, there is a problem that the organic matter is not sufficiently removed, and when the heat treatment silver exceeds 700, the structure of the titanium oxide (Ti0 ₂ ) nanofibers is not maintained. In addition, when the heat treatment time is less than 1 hour, there is a problem that the organic matter is not sufficiently removed, when more than 7 hours there is a problem that the structure of the titanium oxide (Ti0 ₂ ) nanofiber is not maintained.

More specifically, the titanium oxide (Ti0 ₂ ) nanofibers formed through one embodiment of the present invention is a one-dimensional structure, anatase titanium oxide nanofibers (Anatase Ti0 ₂ nano f iber), rutile titanium oxide nanofibers (Rut i le Ti0 ₂ nano f iber), or a combination thereof.

At this time, the anatase titanium oxide nanofibers may be formed by calcining the nanofiber composites at 400-500 for 1-2 hours, and the rutile titanium oxide nanofibers may form the nanofiber composites at 750-800 at 5-7 It can be formed by calcination in time. In addition, when calcined above 500 and below 750, above 1 hour and below 5 hours, titanium oxide nanofibers in which the anatas and rutile phases are mixed are formed. [Form for implementation of invention]

Hereinafter, examples and comparative examples of the present invention are described. However, the following examples are merely examples of the present invention and the present invention is not limited to the following examples. Example

Example 1 (TiO _g nanofiber) Preparation of Titanium Oxide Nanofibers

Titanium isopropoxide (titanium isopropoxide) is added to ethanol and then stirred for 1 hour at room temperature to prepare a first solution. In this process, 25 mol% of acetic acid was added to prevent the precipitation of titanium isopropoxide.

Meanwhile, polyvinyl pyrrol idone, which is an organic substance, is added to ethane, followed by stirring at room temperature for 1 hour to prepare a crab 2 solution. At this time, the concentration of organic matter was adjusted to 5-8 moiy。

Thereafter, the first and second solutions were mixed and then stirred to obtain a homogeneous mixed solution. At this time, the molar ratio of the organic substance to the titanium oxide precursor in the mixed solution was 1/3.

The nanofiber composite was formed through electrospinning with the mixed solution. At this time, the electrospinning condition is 0.5 ml, voltage is 14.5-15.5 kV, the distance between the needle and the aluminum foil to be collected is 9 cm, the needle thickness is 23 gauge It was.

At this time, the nanofiber composite includes an organic material / titanium precursor, and annatase titanium oxide nanofibers (Anatase Ti0 ₂ nanofiber) in which an organic material was removed by calcining at an oxidative atmosphere in the air for 1 hour at 450 was prepared.

On the other hand, the nanofiber composite containing the organic material / titanium precursor can be controlled phase by the calcination temperature and time control. For example, an oxidative atmosphere in the air, and calcined at 750 for 5 hours to prepare rutile titanium oxide nanofibers (Rutile Ti0 ₂ nanofiber) is removed organic matter. In addition, calcining at 700 for 4 hours to prepare titanium oxide nanofibers in which the anatas and rutile phases were mixed. Example 2: Preparation of Lithium-Air Battery

Lithium-air battery manufacturing method using nitrogen-methylpyrrolidone (N-methylpyrrolidone) as a solvent to mix titanium oxide nanofibers, Ketjen black, PVDF-HFP to 40:45:15 ¾> Prepare the electrode for the air battery first. The prepared slurry is thinly coated on carbon paper and then dried at 120 to 5 hours. After drying, the plate is transferred into a glove box and a cell is prepared using a Swazilok-type eel Is. In this case, lithium metal foils are used as counter electrodes, glass fiber disks are used as separators, and 1M LiCF ₃ S0 ₃ is dissolved in tetraethyleneglycol dimethylether as an electrolyte. Used as Finally, the assembled cell is taken out of the glove box, charged with oxygen gas (99.995%) for 10 minutes at 1 sccm, and subjected to electrochemical characterization. evaluation

Experimental Example 1 X-ray Diffraction Analysis

In order to analyze the structures of the anatase titanium oxide nanofibers, and rutile titanium oxide nanofibers of Example 1, X-ray diffraction analysis results are shown in FIG.

Referring to FIG. 1, the anatase titanium oxide is 25.281 degrees 101.

The characteristic peaks at 2 theta angles of 36.946 degrees (103), 37.800 degrees (004), 38.575 degrees (112), 48.049 degrees (200), 53.890 degrees (105) and 55.060 degrees (211) appear. Also, rutile titanium oxide is 2 theta of 27.444 degrees (110), 36.080 degrees (101), 39.203 degrees (200), 41.242 degrees (111), 44.057 degrees (210), 54.330 degrees (211), 56.644 degrees (220) Characteristic peaks appeared at angles (Θ). Experimental Example 2: Scanning electron microscope, transmission electron microscope analysis

Scanning electron microscopy analysis of Anatase titanium oxide nanofibers and rutile titanium oxide nanofibers to analyze the morphology and crystal lattice of the anatase titanium oxide nanofibers, and rutile titanium oxide nanofibers of Example 1 The results are shown in FIGS. 2 and 3, respectively. In addition, the results of transmission electron microscopy analysis of the anatase titanium oxide nanofibers and rutile titanium oxide nanofibers are shown in FIGS. 4 and 5, respectively.

Referring to Figures 2 and 3, the shape of each phase, namely, anatas and tutyl titanium oxide nanofibers is well shown. 4 and 5, it can be seen that both anatas and rutile titanium oxide nanofibers exhibit a one-dimensional shape.

Taken together, it can be seen that titanium oxide nanofibers with well-formed anatase and rutile phases were prepared. Experimental Example 3 Evaluation of Electrochemical Properties

6 to 8 show the results of the electrochemical analysis of the catalytic activity of the anatase titanium oxide nanofibers of Example 1, and rutile titanium oxide nanofibers. ^'

First, a lithium-air battery prepared by the method of Example 2 using the positive electrode active material containing the catalyst is described in 2-4. Layers and discharges were performed at 200 mA / g (carbon) at 5 V, respectively, and measurement results of the charge and discharge characteristics are shown in FIGS. 6 and 7.

Referring to FIG. 6, it shows a potential plane where oxygen and lithium are combined / decomposed during oxygen reduction and evaporation reaction, and shows that the initial capacity of rutile titanium oxide nanofibers is increased as compared to anatase titanium oxide nanofibers. As a control, the evaluation results of the battery prepared without adding the titanium oxide catalyst are also shown.

7 is a differential curve of an initial cycle charged and discharged at 200 mA / g (carbon), respectively, and it can be seen that the overvoltage of the lithium-air battery using the titanium oxide nanofibers of the rutile phase is reduced compared to the anatase titanium oxide nanofibers. .

On the other hand, during layer and discharge at 2 ~ 4.5V, constant voltage was maintained at 4.2V, and the limit was based on carbon weight specific capacity lOOOOmAh / g carbon at 200mA / g (carbon). 20 cycles (cyc le) of layer discharge were performed, and the measurement result of the layer discharge characteristic is shown in FIG. FIG. 8 is a view of capacity-limited lifetime characteristics based on carbon weight specific capacity lOOOOmAh / g carbon), and it is understood that the life of a lithium-air battery using rutile titanium oxide nanofibers is improved compared to anatase titanium oxide nanofibers. Experimental Example 4: Impedance Curve Analysis

After discharging the lithium-air battery prepared in Example 2 at 200 mA / g (carbon), measurement results of Nyqui st characteristics at 0.1-lOOkHz are shown in FIG. 9.

Referring to FIG. 9, as a result of operating the anatase titanium oxide nanofibers and the rutile titanium oxide nanofibers in the same circuit, the rutile titanium oxide nanofibers have a lower band gap than the anatase titanium oxide nanofibers. It can be seen that the charge transfer resistance decreased due to the improvement of e-. From the above results, it can be seen that rutile titanium oxide nanofibers have reduced contact area of oxygen and lithium ions and diffusion distances of lithium ions compared to anatase titanium oxide nanofibers, thereby greatly improving electric conductivity and ion conductivity.

The present invention is not limited to the above embodiments, but may be manufactured in various forms, and a person of ordinary skill in the art to which the present invention pertains does not change the technical spirit or essential features of the present invention. It will be appreciated that the present invention may be practiced as. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

Claims

[Range of request]

[Claim 1]

Adding a titanium ion precursor to the solvent and then stirring to form a first solution;

Adding the organic to the solvent, followed by stirring to form a second solution;

After mixing the first and crab solutions, spinning the mixture solution to form a nanofiber composite; And

Heat treating the nanofiber composite to form titanium oxide (Ti) nanofibers

Method for producing a cathode catalyst for a lithium-air secondary battery comprising a.

[Claim 2]

According to claim 11

After the addition of the titanium ion precursor to the solvent, the step of forming a first solution by stirring; The method of manufacturing a cathode catalyst for lithium-air secondary battery is carried out at room temperature for 0.5 to 2 hours.

[Claim 3]

The method of claim 2,

The titanium ion precursor is selected from the group consisting of titanium isopropoxide, titanium butoxide, titanium chloride, titanium nitride, and titanium carbide. A method for producing a cathode catalyst for a lithium-air secondary battery comprising one or two or more.

[Claim 4]

The method of claim 3,

When the titanium ion precursor is titanium isopropoxide, 20 to 30 mol% of acetic acid (acetic acid) is added to the first solution, the method of manufacturing a cathode catalyst for a lithium-air secondary battery.

[Claim 5]

The method of claim 2,

The solvent is a method for producing a cathode catalyst for a lithium-air secondary battery comprising an alcohol solvent.

[Claim 6]

The method of claim 1,

After adding the organic material to the solvent, and stirring to form a crab 2 solution; is, the method of producing a cathode catalyst for lithium-air secondary battery that is carried out at room temperature for 0.5 to 2 hours.

[Claim 7]

The method of claim 6,

The organic material is a lithium-air secondary that includes one or two or more selected from the group consisting of polyvinyl pyrrol i done, polymethyl methacrylate, and polystyrene. Method for producing a cathode catalyst for batteries.

[Claim 8]

The method of claim 6,

The solvent is an alcohol solvent, acetone (acetone), distilled water (¾0), or a method for producing a cathode catalyst for a lithium-air secondary battery comprising a combination thereof.

[Claim 9]

The method of claim 6,

The molar ratio of the said organic substance with respect to the said solvent is 0.05-0.08 The manufacturing method of the positive electrode catalyst for secondary batteries.

[Claim 10] According to the term 1 l,

After mixing the first and second solutions, spinning the mixed solution to form a nanofiber composite;

Said mixing is a method for producing a cathode catalyst for lithium-air secondary batteries, wherein the molar ratio of the organic matter to the titanium ion precursor is 0.2 to 0.5.

[Claim 11]

The method of claim 1,

The spinning process is performed by electrospinning (electrospinning) method for producing a cathode catalyst for a lithium-air secondary battery.

[Claim 12]

The method of claim 1,

Heat treating the nanofiber composite to form titanium oxide (Ti0 ₂ ) nanofibers; an oxidative atmosphere, and a method for preparing a cathode catalyst for a lithium-air secondary battery, which is performed at 400 to 800 for 1 to 7 hours.

[Claim 13]

The method of claim 12,

The titanium oxide (Ti0 ₂ ) nanofibers have a one-dimensional structure of a cathode catalyst for a lithium-air secondary battery.

[Claim 14]

The method of claim 13,

The nanofibers of the one-dimensional structure may be anatase titanium oxide nanofibers (Anatase Ti0 ₂ nano f iber), rutile titanium oxide nanofibers (Rut i le Ti0 ₂ nanof iber), or a combination thereof. Manufacturing method.

[Claim 15]

The method of claim 14, The anatase titanium oxide nanofibers are prepared by calcining the nanofiber composite at 400 to 500 for 1 to 2 hours.

[Claim 16]

The method of claim 14,

The rutile titanium oxide nanofibers are prepared by calcining the nanofiber composite at 750 to 800 for 5 to 7 hours.

[Claim 17]

The cathode catalyst for lithium-air secondary batteries manufactured by the manufacturing method of the cathode catalyst for lithium-air secondary batteries of any one of Claims 1-16. [Claim 18]

A lithium-air secondary battery positive electrode comprising a cathode catalyst for lithium-air secondary battery according to claim 17;

cathode;

Electrolyte; And

Lithium-air secondary battery comprising a separator.